To date, in a radio communication system in which a gateway apparatus and a plurality of radio stations perform radio communication, the plurality of radio stations have been configured to transmit packets to the gateway apparatus. When the plurality of radio stations and the gateway apparatus directly perform communication, an access method of a radio station is selected based on an error rate of received packets in the gateway apparatus as one mode. Specifically, the gateway apparatus causes the radio station to select a polling access method in the case of high error rate, and to select a random access method in the case of low error rate (for example, Japanese Laid-open Patent Publication No. 8-274788).
On the other hand, when communication is multi-stage relayed by a plurality of radio stations, as one mode, a random access method is used in which a radio station observes a channel empty state by carrier sense, etc., and communication is performed when electric power of a predetermined threshold value or higher is not detected. Specifically, it is difficult for a plurality of radio stations to be synchronized with all the other radio stations included in a radio communication system, and to grasp interference between the radio stations, and thus a random access method is used.
However, in a related-art technique, there is a problem in that the amount of transmission data by a radio station having a plurality of subordinate radio stations becomes large, and thus congestion might occur. Specifically, in a technique in which communication is multi-stage relayed by a plurality of radio stations, a random access method is used. Thus, collisions may become more frequent at a destination of a radio station having a large amount of transmission data. Thereby, resource consumption may increase in a radio band by retransmission of the transmission data, resulting in the occurrence of congestion. It becomes highly possible that such congestion occurs particularly in the vicinity of a gateway apparatus on which data transmitted from radio stations is concentrated.